Automated quill drive assembly for a milling machine

ABSTRACT

An automated quill drive assembly is adapted to be retrofit on a milling machine having a frame presenting a quill head and a quill supported on the head for rotation and for relative shiftable movement along a linear axis between retracted and extended positions. The quill head includes a centrally disposed lower lug, a quill feed engagement control lever boss located above and spaced to one side of the lug, and a transmission cover opening located above and spaced to a side of the lug opposite the quill feed engagement control lever boss. The automated quill drive assembly includes a housing adapted to be mounted to the lug, the quill feed engagement control lever boss, and the transmission cover opening, a motor supported on the housing, and a transmission supported on the housing for transmitting automated movement from the motor to the quill to move the quill between the retracted and extended positions. A sensor is provided for continuously sensing the position of the quill as the quill is moved between the retracted and extended positions. The sensor provides an output signal indicative of the position of the quill for both manual and automated movement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/339,157filed on Jun. 24, 1999, now U.S. Pat. No. 6,357,975 which claims thebenefit of application Ser. No. 09/057,279 filed on Apr. 8, 1998, nowU.S. Pat. No. 5,941,663.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

“Not Applicable”

BACKGROUND OF THE INVENTION

The present invention relates generally to milling machines, and moreparticularly to an automated quill drive assembly that is adapted forretrofitted use on a conventional milling machine to drive Z-axismovement of the quill in response to control from a conventionalcomputer numerical control (“CNC”) controller or the like.

A conventional milling machine, such as a knee mill, includes a table onwhich a work piece can be supported, and a quill that supports a toolfor movement toward and away from the table for milling the work piece.Typically, the table is adjustable within a horizontal plane fromside-to-side and from front-to-back relative to the quill. Lateralside-to-side adjustment is considered X-axis adjustment, andfront-to-back adjustment is referenced as Y-axis adjustment. As such,the position of a work piece can be changed in two planes, and the quillmoves vertically along a Z-axis such that three-axis adjustment of thetool relative to the work piece is possible.

Although many milling machines are manual, in the sense that adjustmentof the table and movement of the quill is manually achieved,improvements in the art have resulted in fully automatic machines inwhich X-axis, Y-axis and Z-axis movement of the table and/or quill arecomputer controlled and carried out by stepper or servo motors. Theseautomatic machines provide many advantages over manual machines,especially with respect to the reproducibility of milling operationsperformed with such milling machines. However, automatic machines lackthe versatility of manual designs, and cost significantly more topurchase and use.

Automated drive assemblies are known that can be retrofitted on anexisting milling machine to automate the X-axis and Y-axis movement ofthe table and the Z-axis movement of the quill. Typically, a CNCcontroller is Wed on the machine at the same time as one or more ofthese drive assemblies such that the drive assemblies are capable ofbeing operated automatically subsequent to installation.

A conventional Z-axis or quill drive assembly broadly includes a housingsupported on the quill head of the machine, a stepper or servo motorsupported on the housing and operatively connected to a conventional CNCcontroller, and a transmission that is supported on the housing andconnected between the motor and the quill to transmit the motor drive tothe quill so that when the motor is operated, the quill is moved betweenthe retracted and extended positions. The housing is secured to the headat three points, one of which is defined by a lower casting lug of thequill head normally used to support a depth stop screw. The second andthird points of attachment of the housing are defined by a pair ofvertically spaced tramming bolts provided along the right front side ofthe quill head.

In the conventional automated quill drive assembly, the position of thequill is continuously monitored by providing feedback from the motor tothe CNC controller indicative of the position or operation of the motor.In addition, limit switches are sometimes employed to provide a positivesignal when the quill is moved to either the fully retracted or fullyextended limit position. In this way, the CNC controller is able tocontrol operation of the motor to accurately position and reposition thequill along the Z-axis during milling operations.

Although conventional automated quill drive assemblies do allow a manualmilling machine to be retrofitted for automatic operation, furtherimprovements would be advantageous. For example, because the housing ofa conventional assembly is mounted to two of the tramming bolts on thequill head, the housing must be loosened in order to tram the head. Suchadded complexity makes tramming of the quill head difficult and timeconsuming.

Further, although tree mounting points are provided for the housing of aconventional quill drive assembly, two of the points are in line withone another vertically, and the third point is spaced laterally from theother two by only 1 to 2 inches. As a result, the motor can twist orwind up when milling a heavy cut, reducing the accuracy of the machine,and increasing wear on the quill.

Another feature of the conventional quill drive assembly subject toimprovement is the source of feedback provided to the CNC controllerwhich allows the position of the quill to be continuously monitored andcontrolled during automatic operation. Because the conventional assemblymonitors quill movement indirectly by sensing motor movement oroperation, the CNC controller can only monitor the quill position whenthe quill is operated by the motor, or when manual quill movement istransmitted back to the motor. As such, manual operation of the quill iseither frustrated or must be performed without the benefit of feedbackto the CNC controller. When manual operation is performed without suchfeedback, depth control and repeatability become difficult to achieve.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automated quilldrive assembly for use with a milling machine, wherein the presence ofthe quill drive assembly does not prevent or impede tramming of thequill head and permits quick conversion between automated and manualoperation of the machine.

It is another object of the invention to provide an automated quilldrive assembly in which the position of the quill is sensed directly,rather than indirectly through a motor, allowing the position of thequill to be continuously displayed by a CNC controller regardless ofwhether quill movement is achieved manually or automatically.

Yet another object of the invention is to provide a quill drive assemblythat can be rigidly secured to the quill head of a conventional millingmachine at three laterally spaced points to fix the motor and othercomponents of the assembly against flexing under the stress of heavymilling operations.

In accordance with these and other objects evident from the followingdescription of a preferred embodiment of the invention, an automatedquill drive assembly is provided that is specially adapted to beretrofit on a milling machine of the category having a frame presentinga quill head and a quill supported on the head for rotation and forrelative shiftable movement along a linear axis between retracted andextended positions. Typically, the quill head of the milling machineincludes a centrally disposed lower lug, a quill feed engagement controllever boss located above and spaced to one side of the lug, and atransmission cover boss located above and spaced to a side of the lugopposite the quill feed engagement control lever boss. Further, themilling machine includes a manually actuated lever supported on the headand operatively connected to the quill for moving the quill between theretracted and extended positions.

The automated quill drive assembly includes a housing adapted to bemounted to the casting lug, the quill feed engagement control leverboss, and the transmission cover opening, a motor supported on thehousing, and a transmission supported on the housing and being adaptedfor connection between the motor and the quill for transmitting drive tothe quill to move it between the retracted and extended positions. Acontroller, such as a CNC controller, is preferably employed with thequill drive assembly for controlling automatic movement of the quill, aswell as for controlling other operations of the milling machine, e.g.X-axis and Y-axis drive assemblies of conventional construction.

In accordance with another aspect of the present invention, theautomated quill drive assembly includes a housing, a motor, atransmission connected between the motor and the quill for transmittingdrive to the quill, and a sensor for continuously sensing the positionof the quill as the quill is moved between the retracted and extendedpositions. The sensor provides an output signal indicative of theposition of the quill for both manual and automated movement, and thesignal can be supplied to a conventional controller to provide a displayof the position of the quill as it is moved.

By providing a quill drive assembly in accordance with the presentinvention, numerous advantages are realized. For example, by providingan automated quill drive assembly that is mounted to the quill head at afirst point of attachment disposed in a vertical plane including thelongitudinal axis of the quill, and at second and third points ofattachment disposed on opposite sides of the vertical plane, theassembly is rigidly secured in place on the quill head, fixing the motorand other assembly components against flexing when a heavy cut is madeor when the quill drive assembly is otherwise placed under stress.

In addition, because the quill drive assembly of the present inventiondoes not employ the existing tramming bolts as mounting points, it isnot necessary to loosen the quill drive assembly or to undertake othercumbersome steps when tramming the head of the milling machine as may berequired for certain operations.

Another advantage achieved by the present invention resides in the useof a sensor that directly senses quill movement rather than motormovement, enabling the controller to provide an indication of quillposition during both automated and manual quill movement. This allows anoperator to control the depth of the quill and to repeat millingoperations with extreme accuracy, even when performing such operationsmanually.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The preferred embodiment of the present invention is described in detailbelow with reference to the attached drawing, wherein:

FIG. 1 is a fragmentary right side elevational view of a conventionalmilling machine;

FIG. 2 is a fragmentary front elevational view of the milling machine,illustrating a quill and quill head forming a part thereof;

FIG. 3 is a fragmentary left side elevational view of the quill andquill head of the milling machine;

FIG. 4 is a perspective view of an automated quill drive assemblyconstructed in accordance with the preferred embodiment of the presentinvention;

FIG. 5 is a fragmentary front elevational view of the automated quilldrive assembly and a conventional computer numerical control assemblymounted on the milling machine;

FIG. 6 is an exploded perspective view of the quill drive assembly,partially broken away to illustrate various components forming a partthereof;

FIG. 7 is a fragmentary right side elevational view of the quill andhead of the milling machine, illustrating the quill drive assemblyassembled on the machine;

FIG. 8 is a fragmentary left side elevational view of the quill and headof the milling machine, illustrating the quill drive assembly assembledon the machine;

FIG. 9 is a fagmenar top plan view of a mounting bracket forming a partof the quill drive assembly;

FIG. 10 is a fragmentary front elevational view of the quill driveassembly, illustrating the quill in a fully retracted position duringautomatic operation of the quill;

FIG. 11 is a fragmentary front elevational view of the quill driveassembly, illustrating the quill in a fully extended position; and

FIG. 12 is a fragmentary front elevational view of the quill driveassembly, illustrating the quill in a fully retracted position duringmanual operation of the quill.

DETAILED DESCRIPTION OF THE INVENTION

A conventional milling machine is shown in FIG. 1, and broadly includesa frame presenting a table 20 and a quill head 22 overlying the table,and a quill 24 supported on the head for rotation and for relativeshiftable movement along the central longitudinal axis thereof towardand away from the table between reacted and extended positions.

The frame includes an upstanding column which supports the quill andhead, and a knuckle 26 supported on the column for pivotal movementabout a transverse, horizontally extending shaft 28. The knuckle issecured in place relative to the column by a plurality of tramming bolts30 which can be loosened to enable the orientation of the knuckle to beadjusted about the shaft The head 22, in turn, is mounted on the knucklefor pivotal movement about a horizontal axis that is perpendicular tothe axis of the shaft 28, and as shown in FIG. 2, a plurality oftramming bolts 32 are used to fix the head relative to the knuckle. Thebolts 32 can be loosened to allow the orientation of the head to beadjusted relative to the knuckle. As such, angular adjustment of thequill about the X and Y axes can be achieved in order to orient thequill at any desired angle relative to the table.

Returning to FIG. 1, a motor 34 is mounted on the head for drivingrotation of the quill, and a manual feed lever 35 is connected to thequill through a rack and pinion quill feed transmission so that when thelever is shifted, the quill is moved between the retracted and extendedpositions. The motor 34 is connected to the quill through a suitabletransmission arrangement for automatically extending the quill when thetransmission is engaged The feed transmission arrangement includes aquill feed engagement control lever 38 that protrudes from a boss 40 onthe right side of the quill head for permitting an operator to engageand disengage the feed transmission, as desired. As shown in FIG. 3, anopening 42 is provided on the left side of the head opposite the quillfeed engagement control lever, and a cover 44 is normally held in placeover the opening by screws that can be removed to allow access to thetransmission components within the head 22. The transmission coveropening 42 is spaced laterally from the quill feed engagement controllever box by about 9 inches, and is also disposed at a height below thatof the boss on the quill head

As illustrated in FIG. 2, the feed transmission of the motor 34 includesa feed kick-out mechanism for disconnecting the quill from the feeddrive of the motor when the quill has been extended by a distance presetby the user. The feed kick-out mechanism includes a depth stop screw 46supported between a pair of cast lugs 48, 50 of the quill head, a depthstop block 52 received around the stop screw and secured to the quillthrough a slot in the head, a travel stop ring 54 threaded onto the stopscrew for adjustment along the length thereof, a kick-out follower 56supported in a sleeve for translational movement, a cam rod 58, and anengagement lever 60. When the quill feed engagement control lever 38 ismoved to the engaged position, the quill is moved automatically towardthe extended position by the motor and the depth stop block 52 travelsalong the depth stop screw 46 until the block engages the travel stopring 54. The force of the block against the ring trips the engagementlever 60 to moves the cam rod 58 upward. The cam rod thus engages thekick-out follower 56, forcing it laterally to a position in which itdisconnects the feed transmission between the motor and the quill. Ascale 61 is mounted along the left side of the depth stop screw 46 toallow a machinist to gauge the depth of the quill, and to set theposition of the travel stop ring 54 so that drive to the quill isdisconnected at the desired depth.

The milling machine thus far described is a conventional knee mill, e.g.of the type manufactured by Bridgeport as a Series 1 type millingmachine. Similar machines are made by several other manufacturers aroundthe world, and the automated quill drive assembly of the presentinvention can be easily adapted for use on any of these conventionalmachines without departing from the scope of the present invention.

Turning to FIG. 4, the preferred automated quill drive assembly is shownprior to assembly on the milling machine. The assembly includes an upperhousing 62, a lower housing 64, a motor 66 supported on the upperhousing, and a transmission adapted for transmitting drive from themotor to the quill of the milling machine.

The upper housing includes a pan 68 having a bottom wall and upstandingfront, side, and back walls, and a cover that protects the componentssupported within the upper housing. The cover is preferably formed intwo pieces 70, 72, wherein the piece 70 supports the motor 66 and isinstalled at the same time as the motor, and the piece 72 is secured tothe pan only after the components within the upper housing have beenassembled. Although not shown, it is possible to provide either or bothof the cover pieces with edges that protrude beyond the side walls ofthe pan such that slots or holes can be formed along the edges of thecover to receive and support tools and the like.

The lower housing 64 includes a pair of angles 74 that together presentthe side and back walls of the lower housing, a pair of laterally spacedchip covers 76 that protrude from the back of the angles to preventchips from betting into the housing during milling operations, and afront cover 78, shown in FIG. 4, fastened to the front edges of theangles. In addition, a bottom plate 80 is secured to the bottom ends ofthe angles for closing off the lower housing from beneath and forholding the angles and the chip covers together as a unit prior toassembly, as shown in FIG. 6.

As shown in FIG. 8, a support arm 82 is provided for supporting theupper housing on the left side of the quill head, and includes a firstend 84 sized for receipt over the transmission cover opening when thetransmission cover is removed from the head, and a second free end 86. Aplurality of trasverse holes extend through the first end of the supportarm 82 for permitting attachment of the arm over the opening in place ofthe transmission cover, and vertical holes are provided at the free end86 for allowing the arm to be fastened to the bottom wall of the pan 68.

As illustrated in FIG. 9, a mounting bracket 88 is provided forsupporting the upper housing on the right side of the quill head, andincludes a base portion 90 and an upstanding portion 92. The baseportion 90 includes a pair of holes or slots for permitting the bracketto be secured to the bottom wall of the pan by suitable fasteners. Theupstanding portion 92 includes a pair of holes or slots that can bealigned with the existing holes in the quill feed engagement controllever boss to permit the bracket to be secured to the boss over thelever when the knob of the lever is removed. Preferably, an additionalthreaded hole in the upstanding portion receives a set screw which canbe tightened down against the quill feed engagement control lever whenthe lever is in the disengaged position such that the lever ispositively locked against movement to the engaged position while thequill drive assembly is installed.

The motor 66 can be either a servo or stepper motor, and is supported onthe cover piece 70 of the upper housing such that an output shaft of themotor is disposed within the housing, as shown in FIG. 5. The motor 66is connected to a power source through a conventional controller, suchas a CNC controller 94 so that operation of the motor can be controlledautomatically. If such a controller is not already provided on themilling machine with which the automated quill drive assembly is to beused, it is assembled on the machine at the same time as the quill driveassembly. It is understood that such controllers are known in the art,and that any conventional type of CNC controller or the like can be usedwithout departing from the scope of the present invention.

As shown in FIG. 6, the transmission of the quill drive assemblyincludes a ball screw 96 supported for rotation about an axis parallelto the axis of rotation of the quill, a ball nut 98 supported on theball screw for movement along the screw when the screw is rotatedrelative to the ball nut, a ball nut block 100 fastened to the ball nutand to the quill, and a belt 102 received over pulleys 104, 106 keyed tothe output shaft of the motor 66 and to the upper end of the ball screw96. As such, rotation of the motor output shaft is transmitted to theball screw 96, axially translating the ball nut 98 along the screw. Theball nut block 100, being secured to the ball nut, also is shiftedaxially, moving the quill between the retracted and extended positions.

Turning to FIG. 10, the ball screw 96 is supported in sealed bearings108 provided in the bottom plate 80 of the lower housing 64 and thebottom wall of the pan 68, and presents an upper end that protrudes intothe upper housing and is keyed to the pulley 106. As shown in FIG. 12,the ball nut is received on the screw for translational movement whenthe screw is rotated relative to the nut, and presents an upper journal110 that is received in the ball nut block 100.

The ball nut block 100 includes a vertical hole within which the ballscrew 96 is received. However, the hole is oversized relative to theball screw so that the block is free to travel along the length of thescrew without engaging the ball screw threads. As such, unless the ballnut block 100 and ball nut 98 are fastened together, the block will notmove as a result of rotation of the ball screw. The rear end of the ballnut block that is fastened to the quill presents a radiused surface thatmatches the radius of the quill so that the block self-aligns with thequill when the block is placed against the quill and fastened in place.

Preferably, the block 100 is fastened to the quill by a socket head capscrew that extends through the block and into an existing threaded holein the quill. In the milling machine as originally constructed, as shownin FIG. 2, the threaded hole receives the depth stop block 52 which isremoved prior to installation of the automated drive assembly. A boreextends through the block 100 from front to back, and is sized forreceipt of the socket head cap screw by which the block is secured tothe quill. The front end of the block is provided with an air gap at thebottom of the bore, and a laterally extending bore extends across thegap for receipt of a socket head cap screw 112. The socket head capscrew can be threaded into the bore to pinch the gap, allowing the blockto be tightened against the journal 110 of the ball nut 98. Preferably,a tubular arm protrudes from the left side of the block in line with thelaterally extending bore so that the socket head cap screw can bedisposed adjacent the side of the lower housing 64. This simplifiesaccess to the socket head cap screw to enable ready conversion betweenautomated and manual modes of operation.

As shown in FIG. 10, a sensor 114 forms a part of the assembly, andincludes a first part 116 fixed to one off the angles 74, a second part118 secured to the ball nut block 100, and a bus or cable 120 connectingthe sensor to an input of the CNC controller. Preferably, the sensor isa linear feedback device such as a conventional glass scale or magneticscale, wherein the first part 116 includes a scale and the second part118 includes a pointer that moves along the scale when the ball nutblock 100 moves relative to the lower housing 64. The sensor 114provides an output signal that is used by the CNC controller incontrolling operation of the motor during automated operation of thequill, and in displaying the position of the quill as it is movedbetween the retracted and extended positions.

Because the sensor 114 is connected to the quill directly through ballnut block 100, it provides a continuous indication of the position ofthe quill regardless of the position of the output shaft of the motor.As such, the sensor outputs an accurate position-indicative signalduring both automated and manual operation that is used by the CNCcontroller to provide a display of the depth or travel position of thequill. The signal is also used by the CNC controller as a feedbacksignal during automated operation to operate the motor.

Although the sensor 114 is illustrated as forming a part of theparticular automated drive assembly shown and described herein, it isunderstood that this arrangement is capable of use on other types andconstructions of automated quill drive assemblies. In addition, thisarrangement of the invention may also have application in a millingmachine that is originally constructed to permit both manual andautomated movement of the quill, and need not be used merely onretrofitted assemblies.

With reference to FIG. 2, prior to installation of the quill driveassembly on a miffing machine, the depth stop screw 46, travel stop ring54, depth stop block 52, engagement lever 60 and scale 61 are removed,as are the knob of the quill feed control lever 38 and the transmissioncover 44. Thereafter, the ball nut block is secured to the quill, andthe lower housing is positioned on the front of the quill head, as shownin FIG. 7, with the bottom plate 80 of the lower housing 64 positionedagainst the underside of the lower front casting lug 50 of the quillhead. A cap screw 122 is inserted through a hole in the bottom plate andthrough an existing hole in the lug 50 through which the depth stopscrew originally extended. A nut is fastened to the cap screw form aboveto fasten the lower housing 64 on the lug 50. Preferably, aninstallation tool is provided to facilitate alignment of the assemblywith the quill head before the nut is tightened fast to the lug. At thesame time of positioning the lower housing relative to the lower castinglug 50, the ball screw is trained through the vertical hole in the ballnut block, as shown in FIG. 6.

Once the lower housing 64 is aligned and secure, the pan 68 is loweredonto the angles 74, aligned with the ball screw 96, and secured in placeby a plurality of cap screws that are passed through holes in the bottomwall of the pan into threaded holes formed in the top edges of theangles. The mounting bracket 88 is then secured in place on the pan 68by fasteners passed through holes or slots in the base portion 90 of thebracket, as shown in FIG. 9. The bracket is secured to the quill feedengagement control lever boss 40 after the lever is moved to thedisengaged position. Fasteners are passed through holes or slots in theupstanding portion 92 of the bracket and threaded into the existingholes in the boss 40.

As illustrated in FIG. 8, the support arm 82 is mounted over thetransmission cover opening 42, shown in FIG. 3, by a plurality offasteners that are passed through the holes in the support arm andthreaded into the existing holes in the quill head 22. Thereafter, asshown in FIG. 6, the support arm 82 is fastened to the pan 68 byfasteners passing through holes in the free end of the support arm andthrough slots formed in the bottom wall of the pan 68. The slots allowthe arm to be aligned with the pan so that the upper housing is securedto the quill head in proper alignment.

With the assembly secured in place on the quill head, the ball screw 96is oriented parallel to the longitudinal axis of the quill, and isspaced from the quill by a distance of approximately 2.75 inches. Byproviding a construction with a ball screw positioned so close to thequill, the moment exerted between the ball screw and the quill isreduced to a minimum. If the ball screw is moved away from the quillaxis, such moments increase, leading to increased wear of the quill andball screw.

The last step of installation of the assembly required in order topermit the assembly to drive the quill automatically is to secure theball nut block 100 to the ball nut 98. As mentioned, and as shown inFIG. 11, the socket head cap screw 112 is provided in the side of theball nut block 100 for tightening the block down against the journal 110of the ball nut 98, and when so fastened together, the quill is tiedinto the transmission for movement with the output shaft of the motor.As such, energization of the motor causes the output shaft to rotate,turning the belt and transmitting the rotation to the ball screw 96. Theball nut 98, which is fixed to the block against rotation relative tothe ball screw, is shifted axially as the screw is rotated, moving theblock 100, and with it the quill, between the retracted and extendedpositions. When the motor turns the output shaft in a first direction,the quill is retracted. When rotated in an opposite direction, theoutput shaft drives extension of the quill.

Operation of the motor is controlled by the CNC controller 94, as shownin FIG. 5, typically as a result of a program set by a series of inputsignals keyed into a keypad 124 by an operator. The signal from thecontroller is delivered to the motor, controlling the direction andduration of its operation. Feedback is constantly provided to thecontroller by the sensor, which provides a continuous indication of theposition or depth of the quill on a display 126 of the assembly 94.

If it is desired to manually operate the quill, the quill is lowered tothe fully extended position shown in FIG. 11 so that the socket head capscrew on the ball nut block is aligned with a hole 128 in one of theangles of the lower housing so that a wrench can be used to loosen thesocket head cap screw 112. As shown in FIG. 8, a small cover 130 isnormally provided over the hole 128 to prevent chips and debris fromentering the lower housing. However, the cover 130 is secured to theangle by a pin which permits the cover to be pivoted from over the holein order to allow access to the socket head cap screw. A small stop 132may also be provided for supporting the cover away from the hole tofacilitate tightening and loosening of the socket head cap screw.

When the socket head cap screw 112 on the ball nut block is loosened,the quill and block are freed for movement independent of the ball screw96 and the motor. As such, manual operation of the quill feed lever 35,shown in FIG. 1, is transmitted directly to the quill 24, and the quillis moved without any binding interference from the ball screw or motor.At the same time, as shown in FIG. 12, because the second element of thesensor is fastened to the ball nut block 100, it continues to provide acontinuous indication of the quill position even though the ball nut 98,ball screw 96 and motor do not move. As such, the CNC controller can beused in the manual mode of operation to display the quill position,enabling a machinist to accurately extend the quill to a desired depth,and to repeat such operations with extreme precision. When the assemblyis to be returned to automated operation, the quill is moved to thefully extended position shown in FIG. 11 and the ball nut block isfastened tight against the journal of the ball nut. A torque wrench isused to insure sufficient holding force, e.g. 20 ft-lbs, between theblock and ball.

With reference to FIGS. 7 and 8, in order to tram the head of themilling machine and angle the quill relative to the table, it is notnecessary to remove the cover 78 of the lower housing or to adjust thequill drive assembly in any way. Rather, the tramming bolts 32 aresimply accessed from the side of the lower housing and loosened,allowing the head to be trammed. Once the position of the head isproperly adjusted, the bolts are simply re-tightened. Thus, tramming ofthe head is not frustrated by the presence of the quill drive assembly.

Although the invention has been described with reference to thepreferred embodiment illustrated in the attached drawing figures, it isnoted that substitutions may be made and equivalents employed hereinwithout departing from the scope of the invention as recited in theclaims.

What is claimed is:
 1. An automated quill drive assembly for use on amilling machine, wherein the milling machine includes a frame presentinga quill head, a quill supported on the head for rotation and forselective movement along a generally vertical axis between retracted andextended positions, and a manually actuated lever supported on the headand operatively connected to the quill for moving the quill between theretracted and extended positions, the automated quill drive assemblycomprising: a housing; a motor supported on the housing; a transmissionsupported on the housing and being adapted for connection between themotor and the quill of the milling machine for transmitting automatedmovement from the motor to the quill to move the quill between theretracted and extended positions; and means for sensing the position ofthe quill as the quill is moved between the retracted and extendedpositions, the sensing means providing an output signal indicative ofthe position of the quill during both manual and automated movement. 2.The automated quill drive assembly of claim 1, wherein the housing ismountable on the milling machine along a rear portion thereof, whereinthe housing includes an opening in the rear portion, and wherein thetransmission is connectable to the quill through the opening.
 3. Theautomated quill drive assembly of claim 2, wherein the transmissionincludes a threaded rod and a block, wherein the rod is rotatablysupported by the housing, wherein the block has a bore therethrough,wherein the block is connectable to the quill, and wherein the block isreceived on the rod via the bore for traveling movement thereon.
 4. Theautomated quill drive assembly of claim 1, wherein the transmissionfurther includes a nut threadably received on the rod and wherein theblock is selectively coupleable with the nut.
 5. The automated quilldrive assembly of claimed 4, wherein the block includes a slot therein,the slot being generally parallel to the bore in the block, wherein theblock includes a transverse bore, wherein the transverse bore receives abolt, wherein tightening the bolt closes the slot and whereby the blockis selectively coupleable to the nut by way of the block clamping on tothe nut when the bolt is tightened.